/**
 * 扩展Date对象的format方法
 */
Date.prototype.format = function(format) {
    var date = {
           "M+": this.getMonth() + 1,
           "d+": this.getDate(),
           "h+": this.getHours(),
           "m+": this.getMinutes(),
           "s+": this.getSeconds(),
           "q+": Math.floor((this.getMonth() + 3) / 3),
           "S+": this.getMilliseconds()
    };
    if (/(y+)/i.test(format)) {
           format = format.replace(RegExp.$1, (this.getFullYear() + '').substr(4 - RegExp.$1.length));
    }
    for (var k in date) {
           if (new RegExp("(" + k + ")").test(format)) {
                  format = format.replace(RegExp.$1, RegExp.$1.length == 1
                         ? date[k] : ("00" + date[k]).substr(("" + date[k]).length));
           }
    }
    return format;
}